Add support for Azure package pools

This adds support for storing packages directly on Azure, with no truly
"local" (on-disk) repo used. The existing Azure PublishedStorage
implementation was refactored to move the shared code to a separate
context struct, which can then be re-used by the new PackagePool. In
addition, the files package's mockChecksumStorage was made public so
that it could be used in the Azure PackagePool tests as well.

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

system/t09_repo/AzureRepoTest_gold

@@ -0,0 +1,5 @@
+Loading packages...
+[+] libboost-program-options-dev_1.49.0.1_i386 added
+[+] libboost-program-options-dev_1.62.0.1_i386 added
+[+] pyspi_0.6.1-1.4_source added
+[+] pyspi_0.6.1-1.3_source added

system/t09_repo/AzureRepoTest_repo_show

@@ -0,0 +1,10 @@
+Name: repo
+Comment: Repo
+Default Distribution: squeeze
+Default Component: main
+Number of packages: 4
+Packages:
+  libboost-program-options-dev_1.62.0.1_i386
+  libboost-program-options-dev_1.49.0.1_i386
+  pyspi_0.6.1-1.4_source
+  pyspi_0.6.1-1.3_source

system/t09_repo/azure.py

@@ -0,0 +1,42 @@
+from azure_lib import AzureTest
+
+
+class AzureRepoTest(AzureTest):
+    """
+    Azure: add directory to repo
+    """
+
+    fixtureCmds = [
+        'aptly repo create -comment=Repo -distribution=squeeze repo',
+    ]
+    runCmd = 'aptly repo add repo ${files}'
+
+    use_azure_pool = True
+
+    def prepare(self):
+        super(AzureRepoTest, self).prepare()
+
+        self.configOverride['packagePoolStorage'] = {
+            'azure': self.azure_endpoint,
+        }
+
+    def check(self):
+        self.check_output()
+        self.check_cmd_output('aptly repo show -with-packages repo', 'repo_show')
+
+        # check pool
+        self.check_exists_azure_only(
+            'c7/6b/4bd12fd92e4dfe1b55b18a67a669_libboost-program-options-dev_1.49.0.1_i386.deb'
+        )
+        self.check_exists_azure_only(
+            '2e/77/0b28df948f3197ed0b679bdea99f_pyspi_0.6.1-1.3.diff.gz'
+        )
+        self.check_exists_azure_only(
+            'd4/94/aaf526f1ec6b02f14c2f81e060a5_pyspi_0.6.1-1.3.dsc'
+        )
+        self.check_exists_azure_only(
+            '64/06/9ee828c50b1c597d10a3fefbba27_pyspi_0.6.1.orig.tar.gz'
+        )
+        self.check_exists_azure_only(
+            '28/9d/3aefa970876e9c43686ce2b02f47_pyspi-0.6.1-1.3.stripped.dsc'
+        )